In today's active lifestyles, people often use more than one computer. Small businesses and even many homes have computers located throughout their premises and connected to one another via a local area network (LAN). Laptops and smaller computing devices, such as personal digital assistants, add to the number of computers that a typical person may use in a day.
This proliferation of computing devices, while providing undoubted advantages, can frustrate a person seeking access to a particular data file. For example, a household has multiple computers for the sake of convenience, but convenience is lost when some files are accessible only from one computer, and other files are accessible only from another. A person can also quickly become confused when faced with multiple versions of the same file. For example, an employee of a small business copies a document from his desktop computer to his laptop. While he travels, he updates the document on the laptop. Other employees do not know where to find the latest version of the document. Indeed, multiple incompatible versions of the document may proliferate throughout the business as several employees update the document without coordinating their efforts. Typically, a person wants to have access to the latest version of a particular data file regardless of where the file may be located and regardless of which computer the person happens to be using at the moment.
Larger businesses have begun to address this issue. Data files are stored on a central server. An authorized user's own computing device requests access to data files residing on the central server by using a service such as Microsoft's “CLIENT-SIDE CACHING.” For added security, the business can have several central servers, each one storing copies of important data files. The central servers coordinate among themselves to ensure that a data file is always available, even when one server is inaccessible for maintenance reasons. From an administrative point of view, centralized data storage eases the tasks of enforcing data access security, of providing enough hardware to store large amounts of data, and of regularly backing up the data. From a user's perspective, centralized storage means that the user always knows where to find a data file, that the data file is essentially always available, and that the latest version of the file is the one presented to the user.
However, centralized data storage comes at a cost. Central servers represent a cost in addition to that of the users' own computers. Configuring and administering a central server environment usually requires special expertise not often found in small businesses or among home owners. People in these smaller environments often object to having a server running at all times because of cost considerations or because of fan noise.